Despite the limited pathogenic effects associated with many Lactobacillus species, probiotic treatment in patients with severe acute pancreatitis increased the risk of bowel ischemia and morality but not infectious complications (Lancet 371: 651; 2008). Since cell wall from Gram-positive bacteria like S. aureus can stimulate systemic inflammation and tissue injury, we investigated whether this could occur with cell wall from Lactobacillus gasseri (L. gasseri), a probiotic microbe. Sprague-Dawley rats were challenged with one of 5 increasing doses (10 to 160 mg/kg) of either S. aureus or L. gasseri cell wall or diluent as 24 hour infusions. The 3 highest doses of both cell walls caused mortality but this was actually greater with L. gasseri. Compared to controls, at 4, 8, and 24 hours during infusions, both cell walls significantly increased lactate, IL-1, IL-10, TNF, MIP-1, RANTES, and nitric oxide levels and decreased circulating neutrophils, lymphocytes and platelets. Compared to the 3 lethal S. aureus cell wall doses, similar L. gasseri cell wall doses caused greater increases in lactate, IL-1, IL-10, TNF, and nitric oxide. Further defining the potential pathogenic effects of cell wall components from probiotic bacteria appears important if such preparations are to be applied in patients predisposed to the translocation of intestinal flora or its products. A manuscript describing this work is in preparation.